Treatment of milk to improve its properties for use in yeast-raised bakery goods



United States Patent 3,518,090 TREATMENT OF MILK TO IMPROVE ITS PROPERTIES FOR USE IN YEAST-RAISED BAKERY GOODS Arthur M. Swanson, Madison, Wis., assignor to American Dry Milk Institute, Inc., Chicago, Ill., a corporation of Illinois No Drawing. Filed Dec. 5, 1967, Ser. No. 688,026 Int. Cl. A23c 9/00 US. Cl. 99-56 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND AND SUMMARY It is desired to employ as much non-fat dry milk in the baking of yeast-raised bread and other bakery goods in order to utilize the nutritional value and the flavor qualities of the milk, but certain factors relating to the loaf volume and fine grain structure thereof have limited the level of such use. In the continuous bread baking method, for example, the normal levels of six percent of the non-fat dry milk cannot be employed; in fact, levels above one to two percent have resulted in weak doughs and bread with poor grain structure and low loaf volume.

I have discovered that certain reactive groups in the micelle of the casein fraction of the milk are primarily responsible for the difliculty in obtaining good loaf volume and fine grain texture. I have further discovered that when the pH of the fluid skim milk, which is normally about pH 6.5-6.6, is adjusted to about 8.5-8.9 and the fluid milk heated at this adjusted pH in the range of 165-210 F. to inactivate the reactive groups in the casein micelle, the difficulty is overcome. The pH of the milk is then readjusted to about its starting pH, and the milk may then be concentrated in vacuum pans and spray-dried or roller-dried, etc. to provide the final product. The non-fat dried milk product thus obtained may be utilized in the continuous bread-making process at the normal level of six percent or higher, and it may be utilized in the baking of any of the yeast-raised bakery goods at even higher levels.

DETAILED DESCRIPTION Tests reveal that the casein fraction of the fluid milk contains factors which are deleterious when the dried milk product is used in bread making. I believe that the micelle of the casein fraction contains reactivegroups which normally resist heating and other treatment, but when subjected to a critically high pH together with heating become inactivated. By heating under alkaline conditions, the micelle seem to open up and expose the reactive groups which are then inactivated by the treatment. When the milk is subsequently readjusted to its original pH and the milk then concentrated and dried by conventional means, a product is obtained which may be employed at high levels in the baking of bread and like yeast-raised goods. t

The fluid milk, which is preferably skim milk, is adjusted to a pH of about 8.5-8.9 and heated to about 165- 210 F. to inactivate the reactive groups in the casein micelle. I prefer to employ a temperature in the range of about 180-195 F. Best results were obtained when the pH was adjusted to 8.7 and the milk heated to 185 F. for a period of 30 minutes.

At the preferred temperature range of l195 F. when the pH is in the range of -89, the time of heating is about 30 minutes. When the temperature is less than 180 F., the time of treatment should be increased to a small extent, and When the temperature is above 195 F., the time is preferably shortened so that, in effect, the heating is equivalent to heating at 185 F. at about 8.7 pH.

The concentrating of the fluid milk may be accomplished by conventional methods, as in a vacuum pan, and drying may be accomplished by conventional systems, such as roller drying and spray drying.

The non-fat dried milk product may be used in sponge and dough procedure, liquid ferment procedure, or in continuous baking procedure, the dried milk product being used at the level of six percent and above, with the bakery products having high loaf volume and fine texture.

In the adjustment of the pH from the normal pH of about 6.5-6.6 to about 8.58.9, any suitable alkaline earth metal hydroxide may be used, as, for example, sodium hydroxide, calcium hydroxide, etc. In adjusting the pH from 8.5-8.9 back to the starting pH, namely, about 6.5- 6.6, any suitable organic or inorganic acid may be used, such as, for example, hydrochloric acid, lactic acid, etc.

Specific examples illustrative of the invention may be set out as follows:

Example I Tests were made utilizing heat alone to determine the effect on the baking properties of non-fat dried milk. The fluid milk was treated at its normal pH and heated to the temperatures indicated in the table below and with the results shown.

The procedure for test baking was based on the method used in the laboratories of American Machine & Foundry. The brew was fermented at 85 F. (29.4 C.) for 2.25 to 2.5 hr. At the end of fermentation the pH was determined and the brew added to the Do-Corder with the mixer blades running at 100 rpm. The remaining flour, sugar, and oxidant were then added. The piston cover was placed in position and mixing was continued for 60 sec. The mixer was then switched to 210 rpm, and mixing was continued /2 a chart min. after the peak was passed. (Chart speed was set at 4 chart min. per min.) The bowl was removed and 19 oz. of dough was carefully scaled into a pan (10 by 4 /2 in. at the top, 9 by 3 /2 in. at the bottom, and 2% in. high) with the minimum amount of handling. The water circulating through the Do-Corder head was adjusted to about 98 F. so that the temperature of the dough at scaling was 104-l05 F. After scaling, the dough was proofed at 100 F. (37.8 C.) and RH. The length of time was equal to the time required to proof the non-milk control, which was run daily, to a height one in. above the pan (measured by template). The dough was then baked in an electric oven at 435 F. for 22 min. After cooling for 1 hr. on the rack, the bread was sealed in plastic bags and judged the following day. This involved determining loaf volume by displacement, weighing, and giving the bread a quality score based on loaf volume, grain, and texture with a maximum of points; 93 points was considered very good, and below 90 points unacceptable.

TABLE I.EFFECT OF FOREWARMING AND CONCENTRATE HEATING AT 175 F. FOR MINUTES ON BAKING PROPERTIES OF NFDM Resist- Adjusted Brew pH Devel- Extensiance to loaf after 2.5 opment bility, extension, Ratio, volume, Bread NFDM sample hours time, sec. mm. B.U. R/E.10 cc./16 02. score No-milk control 4.30:0. 02 =5 125 265 4. 7:0. 7' 2, 570 03:, 5. 10 170 60 28.3 1,837 5.00 88 130 20. 0 2, 37 5.11 60 30 20.6 1,898 85% 5. 12 75 185 90 20. 5 1, 302 86 5.03 00 135 195 6. 0 2, 313 90 5. 10 57 135 240 5. 6 2, 377 90 5.13 55 135 210 5. 4 2, 207 so 5. 10 49 130 260 5. 0 2, 254 90 5. 10 45 125 170 7. 3 2, 207 88 5. 10 42 125 220 5. 7 2,127 88 1 +indicates heat on the concentrate.

The extensibility as set out in the above table was Casein solutions at ad usted pH values were heated at measured inaBra'bender Extensigraph whlch 1s employed 185 F. for 30 minutes, with the results shown 1n to predict the baking properties of batch process dough. Table III.

TABLE III.EFFECT OF HEATING AT 185 F. FOR 30 MINUTES AT ADJUSTED PH VALUES ON BAKING PROPERTIES OF OASEIN SOLUTIONS Resist- Adjusted Brow pH Develop- Extensianee to loaf after 2.5 ment bility, extension, Ratio, volume, Bread pH of heating hours time, sec. mm. B.U. E.l0/R (30/16 oz. score No-milk control 4. s0 40 125 255 4. 7 2, 570 03 6.2 4.80 30 140 170 s. 2 2, 014 00 4. 88 27 135 230 5. 9 2, 040 33 4. s5 30 290 4. 0 2,155 89 4. 90 30 255 4. 7 2, 304 00 s 2 4. 90 27 105 200 3.7 2, 385 02 4 The ElO/R ratio is the ratio of extensibility (E) times -At pH 8.2, grain and texture were equal to those of 10 over the resistance to extension (R). For example, the no-milk control loaf, and the bread was scored only slack or weak doughs show very low resistance to exten- 35 one-half point less than the control because loaf volume sion and generally very high extensibility, resulting in was slightly lower. large E.1()/R ratios. From the foregoing examples, it is shown that the Even with the heating as shown in the above table, the adjusting of the pH of skim milk to the alkaline side of non-fat dried milk reduced the loaf volume at least 200 normal and then heating the same improves considerably cc. and resulted in bread three points or more lower than 40 the baking properties of the final dried product and perthe control. mits the addition of increased amounts of non-fat dried milk in the preparation of yeast-raised bakery goods.

While in the foregoing specification I have set forth The Process was Carried out as flescribed in Example examples in considerable detail for the purpose of illustrat- 1 except that the P of the fluid mllk was adjusted Prior 45 ing embodiments of the invention, it will be understood 2 heating, as shown in Table II belOW- At the P Of that such details may be varied widely by those skilled 8.7 when the milk was heated for 30 minutes at 185 F., in the art without departing from the spirit of my invenan excellent bread score was obtained. tion.

Example H TABLE II.-EFFEOT OF HEATING AT 185 F. FOR 30 MINUTES AT ADJUSTED PH VALUES ON BAKING PROPERTIES OF SKIM MILK Resist- AdIusted Brew pH Develop- Extensiance to loaf after 2.5 ment bility, extension, Ratio, volume, Bread pH of heating hours time, sec. mm. B.U. E.10/R cc./16 oz. score No-milk control 4. 80 40 265 4. 7 2, 570 93 6.2 5.12 43 115 280 4.1 2,123 89 5. 15 30 110 235 4. 9 2, 000 as 5.15 28 105 270 3. 9 2,114 39 5.20 31 120 270 4. 4 2,173 91 5. 17 66 125 225 5. 6 2, 313 91 5 5. 20 03 250 5. 2 2, 433 92 5.28 40 210 7. 1 2, 282 90 As the pH of heating was increased, both loaf volume I claim: and bread score improved until the pH reached a maxi- 1. In a process for treating fluid milk to improve its mum of 8.7. At this level, loaf volume was Within 100 properties for use in yeast-raised bakery goods, in which cc. of that of the control bread and the score was only 65 the micelle of the casein fraction of the milk contains one point less. Heating the skim milk at a higher pH level reactive groups which inhibit loaf volume in baking, the than 8.7 resulted in a poorer loaf of bread. steps of adjusting the pH of the milk to about 8.5-8.9, heating the milk at the adjusted pH to a temperature in Example III the range of about -2l0 F. to inactivate said reactive 70 grou s of the micelle and read'ustin the Tests were made to demonstrate that the heating of its ollaiginal PH J g PH to about h mllk at adlusted PH levels improves baking p p 2. The process of claim 1 in which the temperature is ties of the casems. Casein solutions heated at pH levels b t F, above the normal pH of milk improved loaf volume and 3, Th process f l i 1 i hi h i i after score to a greater extent than heat treatments alone. 75 readjustment of the pH is concentrated and dried.

6 4. In a process for treating fluid milk to improve its OTHER REFERENCES properties for use in yeast-raising bakery goods, the Stamberg et a1 Cereal Chemistry XIX July 1942 steps of adjusting the pH of the milk to about 8.5-8.9, mm

heating the milk at the adjusted pH to a temperature in I n ct P 1 f D Ch tr 10h the range of about 180-195 F. for about minutes, z g g gg g 5 51 n readjusting the pH to about its original pH, and drying Webb et a1 Fundamentals of Dairy Chemistry, The

the milk- A 'P bl I w t t 1965 .s40-545 5. The process of claim 4 in which the milk is fluid v1 u es For Conn (pp skim milk and the pH is adjusted to about 8.7 and the LIONEL SHAPIRO, Primary Examiner milk heated at the adjusted pH to about 185 F. for about 30 i 10 M. NAFF, Assistant Examiner References Cited U S Cl XR UNITED STATES PATENTS 99 54 212 2,671,729 3/1954 Fear et a1, 99-56 

